152 TREES OF THE NORTHERN UNITED SYATES 
There is no attempt in the Key to characterize the hy- 
brids, of which some are quite extensively distributed. 
Quercus heterophylla, Michx. (Bartram’s Oak), supposed to 
be a hybrid between Quercus Phellos and Quercus rubra, 
is found quite frequently from Staten Island southward 
to North Carolina. 
*Cultivated Oaks from the Old World; bark rough; leaves more or 
less sinuated or lobed. (A.) 
A, Acorn cup not bristly...........00- cc cece cee cee eee 20. 
A. Acorn cup more or less bristly.................002 seen 21. 
* Wild species, occasionally cultivated. (B.) 
B. Leaves entire or almost entire, or merely 3- (rarely 5-) lobed 
at the enlarged summit. (C.) 
C. Ends about equal, petioles very short. (D.) . 
D. Leaves small (2 to 4 in. long), evergreen, bark smooth, 
black (Live-oaks) .......... 62... ee cece cee cae 10. 
D. Leaves not evergreen in the North, somewhat awned 
when young, bark very smooth, black and never cracked 
(Willow-oaks). (E.) 
E. Down on the under side quite persistent...... a8, 
E. Under side soon smooth .. ..................00-. 19. 
C. Widened near the tip, somewhat obovate and the end usu- 
ally 3-lobed; bark quite black, smooth or furrowed, but 
never scaly (Black-oaks). (F.) 
F. Leaves acute at base............ ... 0. eee eee eee 16. 
F. Leaves abrupt or cordate at base .................. 17. 
B. Leaves distinctly straight-veined, sinuate rather than lobed, 
the teeth generally rounded and never awned; bark white, 
rough and sealing (Chestnut-oaks). (G.) 
G. Lobes rounded ........ 0 vee ee eee eee cee eee 5, 6, 7. 
G.. Lobes rather'acute 2. ccscsesees o ccsaeeceneieeaeeet 8, 9. 
B. Leaves coarsely lobed, the lobes usually rounded, never 
awned; bark white or whitish-brown, cracking and scaling 
off in thin lamine (White Oaks). (H.) 
H. Leaves crowded at the ends of the branchlets .........4. 
H. Leaves not crowded...... ........... cece eee. 1, 2, 3. 
B. Leaves more or less lobed, the lobes and teeth acute and 
bristle-pointed ; petiole slender; base rather abrupt; bark 
dark-colored, smooth or furrowed, but never sealy (Red 
Oaks). (I.) 
I. Leaves smooth both sides, at least when mature. .11, 12, 13. 
I. Leaves soft-downy beneath........... cccseveeeeee 14, 15. 
